Stabilizing modacrylic fibers with hydroxyphenyl 2h-benzotriazoles



United States Patent 3,383,241 STABILIZING MODACRYLIC FIBERS WKTH HYDROXYPHENYL ZH-BENZOTRIAZOLES Charles W. Davisson, Sr., Charleston, and William R.

Dent, Dunbar, W. Va., assignors to Union Carbide Corporation, a corporation of New York No Drawing. Filed Dec. 3, 1962, Ser. No. 241,549

6 Claims. (Cl. 117138.8)

ABSTRACT OF THE DISCLOSURE Modacrylic fibers made from copolymers of acrylonitrile and vinyl chloride as Well as terpolyrners of acrylonitrile, vinyl chloride and vinylidene chloride are contacted with an aqueous dispersion of a hydroxyphenyl ZH-benzotriazole.

The benzotriazole is concentrated near the surface of the fiber and protects the fiber against degradation by light.

This invention relates to fibers and to a method of improving their stability. It is particularly concerned with the application of stabilizers to synthetic organic fibers in order to improve their stability against deterioration by light, both with respect to color, and physical properties such as tensile strength, resiliency, etc. More particularly, this invention relates to the application of stabilizers from aqueous dispersions to synthetic organic fibers, whereby the stabilizer is sorbed by the fiber, said method being characterized in that said stabilizer will be concentrated in the fiber skin in larger quantities than has heretofore been possible to achieve by the prior art methods.

The technology of fiber production from natural and synthetic organic polymers is Well known. Synthetic organic fibers, for example, are produced by melt spinning (extrusion) of synthetic linear organic polymers through spinnerets, by dry spinning a solution containing the synthetic linear organic polymer, or by Wet spinning a solution of said polymer into a liquid coagulating bath. Color is usually imparted to fibers by standard dyeing methods such as dyeing with disperse dyes, dyeing with cationic dyes, dyeing with acid dyes, etc. As is known, synthetic fibers have found extensive commercial application in the textile industry. However, one important factor in the successful commercial application of these fibers is their stability to light both with respect to color and physical properties. Upon prolonged exposure to sunlight, synthetic fibers are degraded by the ultraviolet rays of light as evidenced by the discoloration of the fibers and the impairment in some of their physical properties, such as, loss of strength, and decreases in elongation, stiffness, resiliency, etc.

Common methods of improving the stability of fibers comprise the addition of so-called stabilizers to the polymer during the spinning operation or in the course of the polymerization reaction. These methods, however, have several disadvantages. To be effective, the stabilizer must be used in relatively large concentrations. Ordinarily, the cost of these stabilizers on a pound per pound basis is considerably higher than the cost of the fibers. Consequently, this method is economically restrictive. In addition, the incorporation of stabilizers in large concentrations in the fiber has been found to have deleterious effects on the mechanical and physical characteristics of the fiber. Also, the addition of stabilizers in the above manner results in the bulk of the stabilizer being in the core of the fiber 3,383,241 Patented May 14, 1968 ICC rather than in the fiber skin where the effect of light is most pronounced, and where the larger concentration is most needed. This phenomenon is further complicated by the fact that in the dyeing operation much of the stabilizer is often leached out and depleted from the fiber, the depletion being greater from the skin than from the core of the fiber. Other methods of application of known internal stabilizers to modacrylic fibers, such as by padding, spraying, milling, etc. have been ineffective.

The application of 2-hydroxy-4-methoxybenzophenone, a commercially known U.V. absorber (stabilizer) to modacrylic fibers, from a dyebath containing said stabilizer, in commercially economical concentrations, shows no improvement in stability of the fibers with respect to discolorations and deteriorations by light. Other commercial benzophenone UV. absorbers are also inelfective when used in economical concentrations. With the increased commercial utilization of synthetic fibers, particularly dyed fibers, the problem of light stability, therefore, is of paramount industrial importance.

It has now been unexpectedly discovered that contacting modacrylic fibers with an aqueous dispersion containing certain stabilizers, which will hereinafter be defined, under operative conditions essentially the same as those employed in standard dyeing operations results in fibers of improved light stability. It has been further discovered that the application of said stabilizers to the fibers can be effected simultaneously with the dyeing of said fibers. Furthermore, it has been unexpectedly discovered that the application of the stabilizer to the fiber by the novel process results in larger concentration of the stabilizer in the fiber skin than in the core of the fiber. As was pre viously pointed out, the larger concentration of the stabilizer in the fiber skin affords greater protection against discoloration and deterioration by light. In the present invention the stabilizer is sorbed by the fiber from the aqueous dispersion containing said stabilizer.

The stabilizers employed in the novel process are the hydroxyphenyl ZH-benzotriazoles having the general formula wherein R can be selected from the group consisting of lower alkyl, lower alkoxyl, lower carboalkoxyl, cyclohexyl, phenyl and hydrogen, m is an integer from O to 3 and n is an integer from 1 to 3. The term lower refers to the number of carbon atoms in said radicals which can range from 1 to 5 and preferably 1 to 3 carbon atoms. Suitable alkyl groups, therefore are methyl, ethyl, propyl, i-propyl, butyl, n-butyl, i-butyl, pentyl, n-pentyl, etc. Examples of stabilizers which can be employed in the present invention are: 2-(2'-hydr0xy-5--nethylphenyl)-benzotriazole, 2-(2- hydroxy-3'-tertiary butylphenyl) 5 chlorobenzotriazole, 2-(2-hydroxy-5-tertiary butylphenyl)-benzotriazole, 2(2 hydroxy-3,5-dimethylphenyl) benzotriazole, 2-(2'-hydroxy-5-amylphenyl)-benzotriazole, 2 (2-hydroxy-3'- methyl-5'-tertiary butylphenyl)-benzotriazole, 2 (2-hydroxy-3,5-dimethylphenyl) S-methoxybenzotriazole, 2- (2-hydroxy-5-methylphenyl)-benzotriazole 5 carboxylic acid butyl ester, 2-(2-hydroxy-3',5',6'-trimethylphenyl)-benzotriazole, and the like. These stabilizers are employed in the bath at concentrations ranging from about 0.01 to about 5.0 weight percent, or more, preferably from about 0.5 to about 3.0 weight percent based on the weight (3) To determine the effect of the dyeing operation on of the fiber. the stabilizer content of the fiber.

TABLE 1 Dyestuti, Dispersant Sodium 28% Diammonium Treating bath 0.5 wt. hexameta- Ammonia, Phosphate, Sulfuric percent Name Wt. phosphate, wt. percent wt. percent Acid percent wt. percent Simulated Dyeing None Dispersant B L.-- 1. 1. 0 Dispersed Dyeing:

0.1. Disperse Blue 27 (10. 1- 0 1. 0 1.0 0.25

0.1. No. 60767. 0.1. 11))isperse Yellow 34 do. 1. 0 Cationic yeing:

. 1.0 1- Ba e 42 g 3 2 5 1.0 CI. Basie Yellow 13 ngfigfigjfi g 0. 5

1 Condensation product of one mole nonylplienol with moles of ethylene oxide. 2 Fatty alcohol amine sulfate.

The novel process is conveniently carried out at opera- 2 The treating procedure, which was the same for all the tive conditions which are essentially the same as those emfibers, is as follows: ployed in standard dyeing operation of the fibers. Thus, A ten gram sample of the fiber was placed in a 500 ml. the temperature can range from about 50 C., or lower, to beaker which contained 300 ml. of the liquid treating bath about 110 C., or higher, and is preferably from about 70 and the bath was heated to its boiling point. After 90 min- C. to about 100 C. The pressure is not narrowly critical utes of heating at the boiling temperature, the fiber was in the invention and it can be atmospheric or superatmosremoved from the beaker and was scoured in a scouring pheric. solution for 10 minutes at 50 C. The scouring solution The time required for the application of the stabilizers consisted of a water bath containing 1 weight percent of a to the fiber depends upon the concentration of the stabidispersant A (condensation product of 1 mole of nonyllizer in the aqueous dispersion, the desired degree of staphenol with 10.5 moles of ethylene oxide) and 0.5 weight bilization, the temperature in the dye bath, the presence or percent sodium hexametaphosphate. The fiber was then absence of carriers in the dye bath, the particular fiber rinsed, centrifuged, dried at 60 C., and thereafter heated which is employed and the quantity thereof, etc. Generally, in a forced-draft oven at 120 C. for 10 minutes. A six this time can vary from about 15 minutes, or less, to about gram sample of this fiber was then carded, pressed into a 10 hours, or more and it is preferably from about 45 minpad between two metal plates which had been heated to utes to about 4 hours. 120 C., and exposed in a Fade-Ometer under standard The equipment employed to carry out the novel process operating conditions. The exposures were made for interof this invention can be conventional dyeing equipment vals of about 20 hours, and successive sections of the fiber such as, for example, dyeing becks, stock dyeing machines, were thus exposed up to a total time of 260 hours, with skein dyeing machines, package dyeing machines, etc. the fiber being inspected visually after each exposure The invention will be more clearly understood with refperiod to observe the discoloration, if any, of each exerence to the following illustrative examples: posed section. h 1

The stability ratings of t e fibers to disco oration by EXAMPLE 1 light were determined by visual inspection of the fibers in A s r s f tests was conducted whereby samples of a combination of daylight and fluorescent light, and the modacrylic fiber (made from a resin consisting of 60% following empirical numbers were adopted as basis of Vinyl chloride and 40% acfyloflitfile) Were treated comparison of the various fiber samples after exposure dividually in separate beakers, each containing a liquid i th F d -0 t i th above manner bath. Thus the fiber samples were treated separately in beakers containing simulated dyeing bath, dispersed dye Vlsual descrIPhOh of dlscolorahoh Nhmerfcal dyeing bath and cationic dye dyeing bath. The composiof fiheri, l'ahhgs tions of said dye baths, not including the stabilizer, are No dlsholorahoh 0 given in Table 1 below. The method of treatment and the h h dlscqloratwn 1 operative conditions were the same for all samples except Sheht dlscolorahoh 5 with regard to (1) the stabilizer content in the fiber sam- 9 of hhahceptahlhty 10 ples, and (2) the type of dyeing baths employed. The deslghlfihaht fhscolorafloh 15 tails are set forth in Table 1. The purpose of these tests, Excesslve dlscolorahoh 20 inter alia, was: Thus an exposure period equivalent to a numerical rating o determine the effect of the Stabiliz of 10 has been adopted as the point of unacceptability, meht oh the dlscolorahoh of the fiber when exposed to i.e., the limit beyond which the fiber becomes unsuitable light, for commercial utilization due to discoloration.

T0 detefmllw the advantages of the appllcatlon Of Table 2 below summarizes the results of the series of stabilizers to the fiber from a liquid bath, and tests which was conducted in this example.

TABLE 2.STABILITY OF FIBER S TO LIGHT Concentration 01' Stabilizer, wt. percent fiber Exposure Time (hours) in Fade-Ometer to Point of Unaeeeptability Test Applied in Applied by Remained after Simulated Disperse Dyeing Cationic Dyeing Manufacture Dyeing B oiling Treat- Dyeing ment Blue Dye 2 Yellow Dye 2 Blue Dye 2 Yellow Dye 2 A.-." 0 0 0 2G 48 35 36 B 0. 50 0 0.17 47 48 65 51 C..." 0 0.50 0.30 55 53 160 60 51 D"... 1. 00 0 0. 24 68 60 80 51 E 0. 50 0.50 0. 46 8O 60 230 65 60 L'lhe stabilizer was 2-(2-l1ydroxy-fi'methylphenyl)benzotrlazole. This stabilizer was added to the liquid bath before heating of said bath. 2 Dyes defined in Table 1.

From Table 2 it will be observed that the depletion (or leaching out) of the stabilizer from the fiber due to the boiling treatment described in this example is greater when the stabilizer has been added to the resin during the manufacture of the fiber than when the stabilizer is added by the method of this invention. Also, the addition of stabilizers to the fiber by the novel process has a marked effect on increasing its stability to discoloration by light. Furthermore, the improvement in color stability of the fiber is more pronounced in the case of addition of stabilizers by the novel process than in the case of incorporation of the stabilizer in the fiber in the spinning operation.

EXAMPLE 2 Ten grams of a modacrylic fiber (made from a resin consisting of 60% vinyl chloride and 40% of acrylonitrile) in the form of 18 denier per filament stable was treated in a liquid dye bath having the following composition.

Material:

Water, ml. 2 (2' hydroxy 5'-methylphenyl)benzotri- Quantity 300 1 Used as carrier for the dye.

In this example as well as the examples which follow all weight percent values are based on the weight of the fiber.

The bath was heated to 80 C, and dyeing was continued for 90 minutes at this temperature. The fiber was then removed from the bath, rinsed, scoured at 50 C., rinsed again, dried at room temperature and relustered by heating in a forced-draft oven at 130 C. for 5 minutes. The scouring solution consisted of water bath containing 1.0 weight percent each of dispersant B and sodium hexametaphosphate respectively. A two grarn sample of this fiber was carded, pressed into a felt between two metal plates that had been heated to 130 C. and was exposed as in Example 1 for 80 hours under standard operating conditions.

EXAMPLE 3 Example 2 was repeated with the exception that the liquid dye bath did not contain the stabilizer, i.e., 2-(2'- hydroxy-5'-methylphenyl -benzotriazole.

The fiber sample exposed in Example 3 was discolored to the point of unacceptability (numerical rating=10.0) in about half the time required for a corresponding discoloration of the sample in Example 2. This indicates that the stability of the fiber to discoloration by light can be markedly improved by the treatment of the fiber with the defined stabilizer by the novel process.

EXAMPLE 4 Example 2 was repeated with the exception that the fiber employed was Verel modacrylic fiber (made from a resin consisting essentially of about 60% acrylonitrile and about 40% of vinylidene chloride).

EXAMPLE 5 Example 4 was repeated with the exception that the stabilizer was omitted from the liquid bath.

It was observed that the sample exposed in Example 4 had reached the point of unacceptability (numerical rating='1 after about 80 hours of exposure in the Fade- Ometer, whereas the sample exposed in Example reached the same point after about 40 hours.

6 Similar results are observed using fibers from a terpolymer of vinyl chloride, vinylidene chloride and acrylonitrile.

EXAMPLE '6 Ten grams of a fiber (made from a resin consisting of 28.5% vinyl chloride, 70% acrylonitrile, and 1.5% sodium methacryloxyethoxybenzene sulfonate) was treated in a liquid dye bath having the following composition:

Materials: Quantity Demineralized =water, m1. 2-(2'-hydroxy 5'-methylphenyl)benzotriazole,

'wt. percent 2.0 Dispersant B, wt. percent 0.5 Dispersant C, wt. percent 0.5 Methyl salicylate, wt. percent 3.0 Cl. Basic Red 22, wt. percent 0.1 Sulfuric acid, sufiicient to give pH=4.0.

Isopropanol, ml. 20

1 Sntficient to make up a volume of 300 ml. 2 Used as carrier for the dye.

The bath temperature was raised to its boiling point (99 C.) and was maintained thereat for 1 hour. The fiber was then removed from the bath, rinsed, scoured at 70 C., rinsed again, centrifuged and dried in a forced-draft oven at 130 C. for minutes. The scouring solution consisted of 300 ml. water, 1.0% dispersant A and 0.5% of sodium hexametaphosphate. A 4 gram sample of the dried fiber was carded, pressed into a pad between metal plates that had been heated to 150 C., and exposed in a Fade-Ometer as in the previous examples for successive periods of about 40, 60, 80 and 100 hours, respectively.

EXAMPLE 7 Same as in Example 6 with the exception that the bath did not contain the stabilizer, i.e., 2-(2'-hydroxy-5'-methylphenyl benzotriazole.

The sample exposed in Example 7 had a point of unacceptability (numerical value of 10) after 55 hours of exposure in the Fade-Ometer, whereas the sample of Example 6 reached the same point after about 70 hours.

EXAMPLE 8 Ten grams of a modacrylic fiber (made from a resin consisting of 60% vinyl chloride and acrylonitrile) in the form of 3 denier per filament tow was added to a beaker containing an aqueous bath having the following composition:

Materials: Quantity Demineralized water, grams 280 2-(2-hydroxy 5-methylphenyl)benzotriazole,

wt. percent 2.0 Dispersant B, wt. per-cent 0.5 Isopropanol, grams 20 The stabilizer was added to the dyebath in the form of a. solution in isopropanol. A fine dispersion of the stabilizer was formed in the aqueous bath in the presence of the dispersant.

The bath temperature was raised to its boiling point (99 C.) and was maintained thereat for 1 hour. The [fiber was then removed from the beaker, rinsed in warm water C. C.), centrifuged and dried in a forcedair oven at C. for 10 minutes. A 5-inch long sample of the dried fiber was placed on a heavy white cardboard and was exposed in a Fade-Ometer for 120 hours.

EXAMPLE 9 Example 8 was repeated with the exception that the stabilizer was omitted from the aqueous bath.

The denier, tenacity and elongation of the fibers of Examples 8 and 9 were measured and the results are summarized in Table 3 below.

TABLE 3 Tenacity, Elongation, Sample Treatment Denier grams per percent denier Before Exposure in None 4.0 2. 5 41. 7

Fade-Ometer. After Exposure in Without 4. O 0. 11 17.9

Fade-Ometer. Stabilizer.

Do With 3.8 1.6 29.4

Stabilizer.

Table 3 shows that the tenacity and elongation of the fiber are retained to a greater extent upon exposure to light by adding the stabilizer in accordance with the process of this invention.

The following example illustrates the effect of varying the concentration of the stabilizer on the light stability of the fiber.

EXAMPLE .10

Ten gram samples of modacrylic fiber (made from a resin consisting of 60% vinyl chloride and 40% acrylonitrile) were added to five separate beakers, each containing a liquid dye bath which was prepared in the following manner.

Three hundred milliliters of water and 1 weight percent each of sodium hexametaphosphate and diammonium phosphate, and 2 weight percent of a red dye (C.I. Disperse Red 35) were added to each beaker. The stabilizer, i.e. 2-(2'-hydroxy-5'-methylphenyl)benzotr-iazole, was added to all, except one, in such amounts so as to give concentrations of 0.5, 1.0, 2.0 and 5.0 weight percent, respectively, based on the weight of the fiber. The stabilizer was added as a dispersion prepared by heating one part of stabilizer and one part of Dispersant B in parts of ethyl acetate (all parts are by weight), until solution occurred. Ninety parts of water was then added to the ethyl acetate solution to produce the dispersion which was then added to the liquid dye bath in amounts sufficient to give the above-stated concentrations in each beaker.

All beakers were heated to the boiling temperatures of their respective liquid dye baths and were maintained at these temperatures for 90 minutes. The fibers were then removed from their respective beakers, and they were scoured in a scouring solution at 70 C. The scouring solution consisted of a water bath containing 1.0 percent each of Dispersant A and 1.0 percent sodium hexametaphosphate. Thereafter, the fibers were rinsed, centrifuged, dried at 60 C. and relustered by heating in a forced-draft oven at 130 C. for 15 minutes.

Exposures of the dried fiber samples in the Fade- Ometer under standard operating conditions indicated that the fiber sample which had been treated with the liquid dye bath without the stabilizer, discolored excessively after 40 hours, Whereas the remaining samples dyed in the presence of stabilizer showed substantially no discoloration at this time. The latter samples, however, showed slight discoloration after 80 hours of exposure in the Fade-Ometer, with the samples treated by the dye baths which contained 2 and 5 percent stabilizer showing the least degree of discoloration. Also, very slight difference in the degree of discoloration was observed between the samples which were treated in dye baths containing 2 and 5 percent stabilizer.

It is therefore observed that the degree of color stability of the fiber to light can be controlled by the concentration of the stabilizer in the dye bath. However, there appears to be a limit of concentration beyond which there is negligible improvement in color stability of the fiber. This limit, of course, depends upon the particular fiber which is treated by the method of this invention. In the case of modacrylic fibers a stabilizer concentration of about 2.0 weight percent (based on the fiber) was found to be the optimum.

Although the invention has heretofore been described with reference to batchwise operation, it is also adaptable to semi-continuous and continuous operations. For example, the fiber may be passed continuously through a liquid bath containing the stabilizer and the dye, and the temperature and residence time controlled so that the stabilizer is sorbed by the fiber in any desired concentration.

The invention is susceptible of many modifications without substantial departure from the spirit of the invention. For example, the invention is equally applicable to fibers which have previously had a stabilizer incorporated therein during the spinning operation or during the manufacture of the resin which is employed in the preparation of the fiber.

It should be emphasized that the novel process improves the stability of the fiber rather than the dye. In fact the improvement in stability of the fiber is independent of the type of dyestuff which is employed in the bath.

Essentially all of the stabilizer that is dispersed in the aqueous bath or the dye bath is sorbed by the fiber and is incorporated therein. As was previously pointed out, however, the application of the stabilizer to the fiber by the novel process results in larger concentrations of the stabilizer in the fiber skin, where it is most needed, to protect the fiber, rather than in the fiber core.

What is claimed is:

1. A process for improving the stability of modacrylic fibers made from copolymers of acrylonitrile and a comonomer selected from the group consisting of vinyl chloride and vinylidene chloride which comprises:

(a) contacting said fiber with an aqueous dispersion containing a stabilizer of the formula wherein R is selected from the group consisting of alkyl containing from 1 to 5 carbon atoms, alkoxyl containing from 1 to 5 carbon atoms, lower carboalkoxyl in which the alkoxy group thereof contains from 1 to 5 carbon atoms, cyclohexyl, phenyl, and hydrogen, m is an integer from 0 to 3 and n is an integer from 1 to 3, and wherein the concentration of said stabilizer in said aqueous dispersion is from about 0.01 to about 5.0 weight percent of said fiber,

(b) maintaining said aqueous dispersion at a temperature ranging from about 50 C. to about 110 C.,

(c) maintaining sufiicient contact time between said fiber and said aqueous dispersion so that said stabilizer is essentially completely sorbed by the fiber and whereby a substantial quantity of said stabilizer is sorbed at the fiber skin, and

(d) recovering and drying said fiber.

2. The process of claim 1 wherein the temperature of said aqueous dispersion is from about 70 C. to about C. and wherein the stabilizer concentration is from about 0.50 to about 3.0 weight percent of said fiber.

3. The process of claim 1 wherein said stabilizer is 2- (2'-hydroxy-5 '-methylphenyl) -benzotriazole.

4. A process for improving the light stability of fibers made from terpolymers of acrylonitrile, vinyl chloride and vinylidene chloride which comprises:

(a) contacting said fiber with an aqueous dispersion containing a stabilizer of the formula wherein R is selected from the group consisting of alkyl containing from 1 to 5 carbon atoms, alkoxyl containing from 1 to 5 carbon atoms, lower carboalkoxyl in which the alkoxy group thereof contains from 1 to 5 carbon atoms, cyclohexyl, phenyl, and hydrogen, m is an integer from 0 to 3 and n is an integer from 1 to 3, and wherein the concentration of said stabilizer in said aqueous dispersion is from about 0.01 to about 5.0 weight percent of said fiber, (b) maintaining said aqueous dispersion at a temperature ranging from about 50 C. to about 110 C.,

(c) maintaining sufficient contact time between said fiber and said aqueous dispersion so that said stabilizer is essentially completely sorbed by the fiber and whereby a substantial quantity of said stabilizer is sorbe-d at the fiber skin, and

(d) recovering and drying said fiber.

5. The process of claim 4 wherein the temperature of said aqueous dispersion is from about 70 C. to about 100 C. and wherein the stabilizer concentration is from about 0.50 to about 3.0 weight percent of said fiber.

6. The process of claim 4 wherein said stabilizer is 2- (2-hydroxy-5 '-methylphenyl) -benzotriazole.

References Cited UNITED STATES PATENTS 9/1962 Boyle 8-61 OTHER REFERENCES Choquette, American Dyestutr Reporter, pp. 681-684, Oct. 15, 1951.

Musgrave, Fibers & Plastics, August 1961, pp. 241- 242.

Coleman, Textile Research Journal, September 1958 pp. 784791 TS 1300 T 33.

Strobel, Amer. Dyestuif Rep., Aug. 7, 1961 pp. 583- 588 TP 890 A 512.

NORMAN G. TORCHIN, Primary Examiner. ART WINKELSTEIN, Examiner.

DONALD LEVY, Assistant Examiner. 

